Replace references to mailing lists to community support and the
Discourse forum.

An initial version of the build documentation for ParaView,
adapted for the wiki. It will definitely need expansion as
we try it out and find necessary pieces for current ParaView.

Also added steps and a link for building ParaView.

Updating contributing and developing guides to include changes to
issues tracker and merge request workflows.

Currently, there are no formal requirements for commit messages.
This is a step toward requirements without getting too formal.

The Documentation/dev/git/README.md document is the main dispatch
point for documentation of ParaView Git infrastructure.  We should
link to it from the contribution guidelines document.

Robert Maynard authored Mar 30, 2015 and Brad King committed Apr 02, 2015

The actual documentation for contributing to ParaView is buried inside
the fourth link when browsing the ParaView project. This adds a stripped
down version of how to contribute to the main CONTRIBUTING, and which
links directly to the subsections of develop.md that document each step
of the process.

Add a README.md, CONTRIBUTING.md and Copyright.txt with some basic text
inspired from VTK's versions of the same.